Web app performance in iOS 4 has been disappointing. It’s been speculated that Apple has been intentionally handicapping web app performance in iOS 4. When websites are launched from the iPhone’s homescreen, loading times become much longer than when a site is opened straight from the Mobile Safari app.

In iOS 5, it’s been discovered that fullscreen web apps from the homescreen can access the Nitro Javascript engine that sped up Mobile Safari in iOS 4.3. These “dynamic-codesigning” privileges allow for a much faster web app experience in iOS 5.

For some reason, web apps launched from a homescreen shortcut in iOS 4.3 fail to use the Nitro engine that is available when regularly browsing in Mobile Safari. This means that visiting websites through shortcuts can result in much longer load times than the traditional method in Safari itself.

CNET discovered that this bug has been fixed in iOS 5 Beta 1, and that Nitro JavaScript engine access is now disclosed to the Web.app feature. We showed you a roundabout way to speed up web apps in iOS 4, but it looks as though that method will be unnecessary when iOS 5 drops this Fall.

Although unconfirmed, it was speculated that Apple was hindering web app performance (prior to iOS 5) in an attempt to handicap apps that didn’t come from the App Store. If that’s the case, it looks like Apple got the message and fixed the problem in iOS 5.

If you’re got the iOS 5 beta, have you noticed a performance improvement in web apps launched from the homescreen?